The present invention generally relates to the field of plasma processes and, more particularly, to detecting leaks in systems utilized to perform such plasma processes.
Plasma is used in various types of industrial-type processes in the semiconductor and printed wiring board industries, as well as in various other industries such as in the medical equipment and automotive industries. One common use of plasma is for etching away materials in an isolated or controlled environment. Various types of materials may be etched by one or more plasmas, including glasses, silicon or other substrate materials, organics such as photoresist, waxes, plastics, rubbers, biological agents, and vegetable matter, and metals such as copper, aluminum, titanium, tungsten, and gold. Plasma is also utilized for depositing materials such as organics and metals onto an appropriate surface by various techniques, such as via chemical vapor deposition. Sputtering operations may also utilize plasmas to generate ions which sputter away material from a source (e.g., metals, organics) and deposit these materials onto a target such as a substrate. Surface modification operations also use plasmas, including operations such as surface cleaning, surface activation, surface passivation, surface roughening, surface smoothing, micromachining, hardening, and patterning.
Plasma processes are typically conducted in a highly controlled environment, such as a sealed processing chamber. It is thereby desirable to avoid an introduction of impurities (e.g., air and/or water vapor) into the plasma processing system since any such impurity may have an adverse effect on one or more aspects of the plasma process. By way of example, impurities may enter a plasma processing system through one or more leaky seals. One conventional way in which at least the potential for leaks is detected is by monitoring pressure within the processing chamber. In the event that the system will not hold a vacuum or pressure at a desired level, an assumption may be made that this is due to an existence of one or more leaks. How the location(s) of these leaks is identified is typically quite cumbersome. Upon discovering that the system will not hold a vacuum or pressure at a desired level, a chamber of the plasma processing system is shut down (i.e., taken off line). The plasma processing system is subsequently xe2x80x9copenedxe2x80x9d to allow leak detection equipment (e.g., mass spectrometer) to be incorporated in an appropriate flow path. Thereafter, the system is once again sealed and helium is applied on one or more seals on the exterior of the system to detect a presence of helium within the corresponding chamber of the plasma processing system via the installed leak detection equipment. While such a leak detection protocol may enable leak detection, shut down of the system (sometimes accompanied by evacuation of the plasma from the system) typically results in fiscal and/or temporal inefficiency. It would thus be desirable to provide a leak detection system that increases the potential for minimizing and/or alleviating one or more of the above-mentioned drawbacks associated with conventional leak detection systems.
Accordingly, the present invention is generally directed to detection of leaks in a plasma system. Moreover, the present invention allows for accomplishing such leak detection while maintaining a plasma within the plasma system and optionally while a product (e.g., a wafer) is positioned within the corresponding plasma chamber. Herein, xe2x80x9cmaintainingxe2x80x9d a plasma in the plasma system refers to avoiding intentional removal of the plasma from the plasma system. In other words, the plasma is generally not removed from the plasma system prior to leak detection. As another potential benefit, the present invention may be a portable (i.e., handheld) assembly for conducting such leak detection. Accordingly, when analysis of the plasma is desired to check for the presence of a leak, this portable device may simply be pointed at and looking through a window of the plasma system. Herein, xe2x80x9cportable,xe2x80x9d xe2x80x9cportability,xe2x80x9d and the like generally refer to a characteristic of the associated leak detection assembly which enables the same to be freely moved and/or carried about by a potential user. In other words, a potential user (e.g., engineer, operator, technician, or the like) may be able to carry a leak detection assembly of the invention with him/her in a tool box or on his/her clothing (e.g., on a tool belt or supported by a shirt/pant pocket).
A first aspect of the invention is generally embodied in a method of detecting a leak in a plasma system. This method of the first aspect generally includes maintaining a plasma in the plasma system and obtaining optical emissions spectral data of the plasma within the plasma system at least at a plurality of times while maintaining the plasma in the plasma system. The method also includes monitoring for an existence of air in the plasma while both maintaining the plasma in the plasma system and obtaining optical emissions spectral data of the same. If air is identified in the plasma, a first external surface of the plasma system is exposed to a test gas while maintaining the plasma in the plasma system. Optical emissions spectral data of the plasma can then be analyzed for the presence of the test gas (e.g., helium, neon, and/or argon) to determine if the first external surface to which the test gas was exposed is the location of the leak.
Various refinements exist of the features noted in relation to the subject first aspect of the present invention as well. Further features may also be incorporated in the subject first aspect of the present invention as well. These refinements and additional features may exist individually or in any combination. For example, monitoring the plasma for the existence of air may include comparing the optical emissions spectral data of the plasma with predetermined optical emissions spectral data of air. Moreover, the optical emissions spectral data indicative of air may be acquired and stored on a computer-readable storage medium (e.g., E-PROM, a floppy disk, compact disk, hard disk) to be utilized during monitoring the plasma for the existence of air.
Some embodiments in the case of the first aspect may include exposing a second external surface (i.e., different from the first external surface) of the plasma system to the test gas upon failing to identify a presence of the test gas in the plasma after the first external surface was exposed to the test gas. In other words, if the test gas is not detected within the plasma system within a reasonable time after exposing the first external surface to the test gas, the first aspect may include exposing the second external surface of the plasma system to the test gas. Upon exposure of the second external surface of the plasma system to the test gas, the plasma is once again analyzed to determine if the test gas is present therein. This may be repeated until the leak has been located or until all external surfaces have been tested in this general manner. In some embodiments, any product (e.g., a wafer or chip precursor) originally disposed within the plasma system may be removed prior to exposing any external surfaces of the plasma system to the test gas. However, other embodiments provide for any product originally disposed within the plasma system to remain there while the external surface(s) is exposed to the test gas. In other words, in these other embodiments, a product may be located within the plasma system, and a plasma process may be running while the external surface(s) is exposed to the test gas for leak detection purposes.
In the case of the first aspect, a leak detector may be utilized for comparing the optical emissions spectral data of the plasma with spectral data of air stored on the leak detector and/or for comparing the optical emissions spectral data of the plasma with spectral data of the test gas stored on the leak detector. So, the leak detector may operate in a first mode to detect the presence of air within the plasma and a second mode (different from the first mode) to detect the presence of the test gas within the plasma. By way of example, the leak detector of this first aspect may have a switch on it. When the switch is in a first position, the leak detector may compare the optical emissions spectral data of the plasma with a spectral pattern of air stored on the leak detector. Likewise, when the switch is in a second position, the leak detector of this first aspect may compare the optical emissions spectral data of the plasma with a spectral pattern of the test gas stored on the leak detector. Various features discussed above in relation to the first aspect of the present invention may be incorporated into any of the following aspects of the present invention as well, and in the manner noted above.
A second aspect of the invention is also embodied in a method of detecting a leak in a plasma system. The method of this second aspect of the present invention includes maintaining a plasma in the plasma system, and obtaining optical emissions spectral data of the plasma at least at a plurality of times while the plasma is maintained in the plasma system. This second aspect further includes comparing the optical emissions spectral data of the plasma with a predetermined spectral pattern indicative of optical emissions spectral data of air. If the comparison results in a determination that the optical emissions spectral data of the plasma includes a pattern that matches the predetermined spectral pattern of air, an assumption can be made that the plasma system has a leak. Herein, xe2x80x9cmatchesxe2x80x9d refers to the pattern resembling or having similar characteristics (e.g., the presence of peaks at similar wavelengths) of the predetermined spectral pattern of air. To discover the location of the leak, an external seal of the plasma system is exposed to a test gas and the optical emissions spectral data of the plasma is analyzed for a presence of the test gas. If the test gas is determined to be present in the plasma, an assumption can be made that the external seal that was exposed to the test gas is where the leak can be found.
Various refinements exist of the features noted in relation to the subject second aspect of the present invention. Further features may also be incorporated in the subject second aspect as well. These refinements and additional features may exist individually or in any combination. For example, the predetermined spectral pattern of air utilized by this second aspect may include a plurality of, and even substantially all, wavelengths between 250 nm and 790 nm. The second aspect may include determining if the optical emissions spectral data of the plasma includes each spectral peak associated with air, or at least 33% of all spectral peaks associated with air. Various features discussed above in relation to the second aspect of the present invention may be incorporated into any of the other aspects of the present invention as well, and in the manner noted above.
A third aspect of the present invention is also embodied in a method of detecting a leak in a plasma system. This third aspect includes maintaining a plasma in the plasma system and obtaining optical emissions spectral data at least at a plurality of times while the plasma is maintained in the plasma system. Moreover, this third aspect includes both identifying an existence of an air leak and determining a location of the leak from the obtained optical emissions spectral data. Various features discussed above in relation to the first and second aspects of the present invention may be incorporated, individually or in any combination, into this third aspect as well, and in the manner noted herein.
A fourth aspect of the present invention is embodied in a leak detection assembly for use in combination with a plasma system. This leak detection assembly includes a spectrometer, and a memory including optical emissions data of air and optical emissions data of a test gas. The leak detection assembly also includes a logic circuit or the like capable of comparing the optical emissions data of the memory with optical emissions data obtained from the plasma system by the spectrometer. In addition, this leak detection assembly generally is equipped with a switch. When this switch of the leak detection assembly is in a first position, the logic circuit is capable of comparing the optical emissions data of air with the optical emissions data obtained from the plasma system by the spectrometer. Likewise, when this switch is in a second position, the logic circuit is capable of comparing the optical emissions data of the test gas with the optical emissions data obtained from the plasma system by the spectrometer.
Various refinements exist of the features noted in relation to the subject fourth aspect of the present invention. Further features may also be incorporated in this fourth aspect of the present invention as well. These refinements and additional features may exist individually or in any combination. Some embodiments of this fourth aspect include a housing. The optical emissions spectrometer, the memory, and the logic circuit of the leak detection assembly may be substantially positioned within this housing. To quantify the portability of some embodiments of the fourth aspect, this housing may have a volume (i.e., three-dimensional space enclosed within or occupied by the housing) of no more than about 192 cubic inches (in3) in one embodiment, and no more than about 40 in3 in another embodiment. As another avenue of quantifying the portability of some embodiments of the fourth aspect, the leak detection assembly may exhibit a weight of no more than about five pounds in one embodiment, and no more than about one pound in another embodiment. So, some embodiments of this fourth aspect may be handheld, or capable of being entirely supported by the hands of a user. However, other embodiments of this fourth aspect may exhibit leak detection assemblies having one or both a weight and a volume greater than that disclosed above.
In the case of this fourth aspect of the present invention, a variety of other components may be included in the leak detection assembly. For example, the leak detection assembly may be equipped with an indicator for providing an indication that the leak detection assembly has detected air and/or the test gas within the plasma system. This indicator may be designed to emit a first signal upon detection of air and to emit a second signal (different than that of the first) upon detection of the test gas. Any mechanism(s) capable of emitting one or more appropriate signals such as sound, light, and/or vibrations may be suitable as the indicator. As another potential component, a trigger may be included in the leak detection assembly, wherein activation (e.g., pressing, squeezing, pulling, flipping, and the like) of this trigger may initiate collection and/or analysis of the optical emissions data. As still yet another potential component, the leak detection assembly may include a mounting structure configured to enable the same to be mounted on the plasma system. In other words, this mounting structure generally allows the leak detection assembly to be releasably attached to the plasma system, for example, to allow optical emissions spectral data to be obtained through a viewing window (or the like) of the plasma system.
Yet a fifth aspect of the present invention is embodied in a leak detection assembly having a first mechanism for collecting optical emissions data of a plasma, a memory that includes optical emissions data of both air and a leak detection gas, and a second mechanism for comparing the optical emissions data of the plasma with both the optical emissions data of air and the optical emissions data of the leak detection gas. Various features discussed above in relation to any of the aspects of the present invention may be incorporated, individually or in any combination, into this or any other aspect of the invention, and in the manner disclosed herein.